1. Technical Field
The present disclosure relates to a cathode active material for a nonaqueous electrolyte secondary battery, a nonaqueous electrolyte secondary battery, and a method of producing a cathode active material for a nonaqueous electrolyte secondary battery.
2. Description of the Related Art
Lithium ion batteries have high capacities and high energy densities, and can be easily miniaturized and reduced in weight. Accordingly, for example, a demand for lithium ion batteries has been increasing in power sources for portable small electronic equipment and electric vehicles.
In development of lithium ion batteries, an increase in capacity is an important technological issue, and a Li2MnO3—LiMeO2 solid solution cathode material has attracted attention as a high-capacity material. In this chemical formula, Me represents a metal element. This solid solution cathode material utilizes not only the redox reaction of manganese (Mn) and the metal element, but also the redox reaction of oxygen. As a result, the solid solution cathode material has a higher discharge capacity than traditional laminar lithium-cobalt oxide. Japanese Unexamined Patent Application Publication No. 2012-234772 discloses a solid solution cathode material having an O3 structure prepared by direct lithiation. Japanese Unexamined Patent Application Publication No. 2012-204281 discloses a solid solution cathode material having an O2 structure prepared by ion exchange of NaxLiyMeO2 having a P2 structure. The O2 structure, O3 structure, and P2 structure represent the structures of oxygen atoms located around lithium atoms and the numbers of cycles of the laminar structures, where O represents an octahedron structure; P represents a prism structure; and 2 and 3 represent the number of cycles of each layer.